Access to the left side of the heart plays an important role in the diagnosis and treatment of cardiovascular disease. Invasive cardiologists commonly perform a left heart catheterization for angiographic evaluation or transcatheter intervention of cardiac or coronary artery disease. In a left heart catheterization, the operator achieves vascular access through a femoral artery and passes a catheter in a retrograde direction until the catheter tip reaches the coronary artery ostia or crosses the aortic valve and into the left ventricle. From a catheter positioned in the left ventricle, an operator can measure left ventricular systolic and end-diastolic pressures and evaluate aortic valve disease. Ventriculography, where contrast is injected into the left ventricle, may be performed to evaluate left ventricular function. Alternative insertion sites, such as the brachial or radial artery, are used sometimes when femoral artery access is contraindicated due to iliofemoral atherosclerosis, but manipulation of the catheter can be more difficult from these other insertion sites.
Although left heart catheterization can be a fast and relatively safe procedure for access to the coronary arteries and the left ventricle, its usefulness for accessing structures beyond the left ventricle, namely the left atrium and the pulmonary veins, is limited by the tortuous path required to access these structures from the left ventricle via the mitral valve. For example, electrophysiologic procedures requiring access to the left atrium or pulmonary veins, performance of balloon mitral valve commissurotomy, and left ventricular access across an aortic prosthetic disc valve can be difficult, and sometimes unfeasible, through traditional left heart catheterization techniques.
Transseptal cardiac catheterization is another commonly employed percutaneous procedure for gaining access to the left side of the heart from the right side of the heart. Access occurs by transiting across the fibro-muscular tissue of the intra-atrial septum from the right atrium and into the left atrium. From the left atrium, other adjoining structures may also be accessed, including the left atrial appendage, the mitral valve, left ventricle and the pulmonary veins.
Transseptal cardiac catheterization has been performed in tens of thousands of patients around the world, and is used for both diagnostic and therapeutic purposes. Diagnostically, operators utilize transseptal catheterization to carry out electrophysiologic procedures requiring access to the pulmonary veins and also to do left heart catheterizations where a diseased aortic valve or an aortic disc prosthetic valve prohibits retrograde left ventricular catheterization across the valve. Therapeutically, operators employ transseptal cardiac catheterization to perform a host of therapeutic procedures, including balloon dilatation for mitral or aortic valvuloplasty and radiofrequency ablation of arrhythmias originating from the left side of the heart. Transseptal cardiac catheterization is also used to implant newer medical devices, including occlusion devices in the left atrial appendage for stroke prevention and heart monitoring devices for the treatment of cardiovascular disease.
The vast majority of transseptal procedures is performed via a femoral vein access site, using special set of devices, called a Brockenbrough needle and catheter/dilator, designed for this approach. In this standard approach the Brockenbrough catheter/dilator, with the hollow Brockenbrough needle within, is advanced from a femoral vein, through the inferior vena cava, through the right atrium and into the superior vena cava. The distal end is then pulled back to the right atrium and rotated until it points at the foramen ovale of the atrial septum. The Brockenbrough needle has a gentle bend that facilitates guiding the system from the vena cava into and through the right atrium, to the intra-atrial septum. The right atrial surface of the septum faces slightly downward, toward the inferior vena cava, so that the natural path of the Brockenbrough needle/catheter brings it to the atrial surface at nearly a right angle of incidence. After verifying the location of the catheter tip at the septal surface by fluoroscopy and/or ultrasound imaging, the operator can firmly but gradually advance the needle within the catheter until its tip penetrates the septum. Contrast material is then injected through the lumen of the Brockenbrough needle and observed fluoroscopically to verify placement of the tip in the left atrium. Once this placement is verified, the catheter/dilator may be advanced through the septum into the left atrium, the Brockenbrough needle is removed and a guide wire can be placed into the left atrium through the dilator lumen. At this point, access to the left atrium has been established and the Brockenbrough needle can be removed, allowing introduction of other devices either over the guide wire or through a Mullins sheath placed over the dilator, or both, as is well known to those skilled in the art.
Transseptal cardiac catheterization using the standard technique described above is generally successful and safe when performed by skilled individuals such as invasive cardiologists, interventional cardiologists, and electrophysiologists with appropriate training and experience. Lack of success may be attributable to anatomic variations, especially with respect to the size, location and orientation of the pertinent cardiovascular structures and imaging-related anatomic landmarks. Another reason for failure may be the relatively fixed dimensions and curvatures of currently available transseptal catheterization equipment. One major risk of existing transseptal catheterization techniques lies in the inadvertent puncture of atrial structures, such as the atrial free wall or the coronary sinus, or entry into the aortic root or pulmonary artery. In some cases, these punctures or perforations can lead to bleeding around the heart resulting in impaired cardiac function known as cardiac tamponade, which if not promptly recognized and treated, may be fatal. As such, surgical repair of such a cardiac perforation is sometimes required.
One problem with the standard transseptal needle/catheter system is that once an inadvertent puncture has occurred, it may be difficult to realize what structure has been compromised because contrast injection through the needle is limited by the small bore lumen thereof. Thus, visualization of the structure entered may be inadequate and non-diagnostic. Also, the tip of the catheter dilator of existing devices may cross the puncture site which has the effect of further enlarging the puncture hole.
Other than minor refinements in technique and equipment, the standard transseptal catheterization procedure has remained relatively constant for years. Even so, the technique has several recognized limitations that diminish the efficacy and safety of this well-established procedure. Thus, there remains a need for an alternative system that effectively and safely provides access to the left atrium, or other desired site in the body.
As noted above, standard transseptal cardiac catheterization is performed via the inferior vena cava approach from an access site in a femoral vein. In some situations it is clinically desirable to perform transseptal cardiac catheterization via the superior vena cava from an access site in a vein in the neck or shoulder area, such as a jugular or subclavian vein. The superior vena cava approach is more problematic than the standard inferior vena cava approach because of the downward anatomical orientation of the intra-atrial septum, mentioned above: the Brockenbrough needle must make more than a 90° bend to engage the atrial septum at a right angle of incidence, which makes it difficult to exert a sufficient force along the axis of the needle to penetrate the septum. In fact, it is in general problematic to exert an axial force around a bend in a flexible wire, rod, needle, or other elongated member, because the axial force tends to bend or flex the device rather than simply translate it axially. Thus, there is a need for improved apparatus and methods for performing procedures requiring an axial force, such as punctures, when a bend in the flexible member transmitting the force is unavoidable. Another problem not infrequently encountered with conventional transseptal catheterization is that advancement of a Brockenbrough needle against the septum can cause substantial displacement or tenting of the septum from right to left prior to puncture. Sudden penetration can result in the needle injuring other structures in the left atrium. Two approaches to these needs are addressed in this invention: reduction or elimination of the force required to perform the procedure, such as a transseptal puncture; and provision of a stabilizing apparatus for transmitting an axial force around a bend.